When operating radio network equipment, such as evolved nodeB (eNodeB), it is desirable to calculate a metric of the channel quality so that channel errors due to noise, modulation errors, etc., can be quantified. One typical metric of channel quality is the error vector magnitude (EVM). The error vector magnitude is a ratio of the power of an error vector from a received signal to an ideal signal and the power of the ideal signal. Noise, distortion, spurious signals, and phase noise all degrade the EVM, and thus the EVM provides a comprehensive measure of the quality of the radio receiver or transmitter for use in digital communications.
The EVM is typically calculated during transmission of user data. In order to calculate the EVM, a signal is received and demodulated. The demodulated signal will correspond to a constellation point in the IQ plane. The error vector is the vector from the ideal constellation point to the actually received constellation point. The vector magnitude can then be computed from the ratio of the power of the error vector to the power of the ideal constellation point.
Because conventional error vector magnitude calculation relies on user data, conventional EVM calculation requires user equipment (UEs) to be communicating user data with the eNodeB. However, it may be desirable to determine an indication of the error vector magnitude prior to the transmission of user data so that the health of the eNodeB can be assessed before the eNodeB is ready or capable of transmitting user data or synchronization data. Conventional EVM calculation that relies upon user data is unable to perform such a pre-user communication health check of the eNodeB.
Accordingly, in light of these difficulties, there exists a need for methods, systems, and computer readable media for determining a metric of radio frequency channel quality in terms of error for idle channels.